The publication of the special edition “Enquêter en milieu difficile” (Revue Française de Sciences Politiques, 1, 2007) during the last months of my Phd was a revelation. Working on the local regulation of Islam, I was dealing with the retranscription of a difficult, sensitive and very political fieldwork. The discovering of this literature helped me to bring ethnography back in my own research. What I intend to do in this contribution is to address, firstly, how I have used ethnographic observations to invest my fieldwork about the installation of mosques in the Brussels public space and, secondly, to present some observations about theoretical and methodological considerations about my inductive approach and my case study.